The present invention relates to a new and distinctive sorghum hybrid, designated CB 7520. All publications cited in this application are herein incorporated by reference.
The new sorghum hybrid CB 7520, also known as ES5200, can be used as a biomass feedstock crop for biofuel and/or biopower applications. Sorghum hybrid CB 7520 may be grown for biomass, sugar, and/or forage.
As a biomass crop, sorghum can be of any of the many varieties which have a high biomass. Many of these varieties are photoperiod sensitive and do not flower when grown in temperate latitudes. The continuous growth of vegetative biomass uninterrupted by flowering allows these varieties to produce significantly more vegetative biomass in comparison to grain sorghums. These high biomass sorghum varieties and hybrids also comprise genetic backgrounds that have been selected for based on increased plant height, increased biomass, increased growth rate, and lack of dwarfing genes, among other traits.
As a sugar crop, sorghum can be of any of the many varieties which have a high sugar content. Stalks are used for producing biofuel by squeezing the juice and then fermenting the juice into a liquid biofuel, such as ethanol. Varieties of sorghum grown for sugar content can be open-pollinated varieties or hybrids. In addition to squeezing stalks for juice, sorghum biomass may be treated with chemicals or industrial processes to release simple and complex sugars which can then be used in biofuel production. Varieties of sorghum grown for sugar content can be characterized by high brix values or by other more refined measurements of sugar components.
As a forage crop, the genus Sorghum includes three principal distinct morphotypes that are used as forages: forage sorghums, sudangrass, and sorghum×sudangrass hybrids. These three morphotypes have grossly different phenotypes and different modes of principal utilization. Forage sorghums have very coarse stems and wide leaves, similar to corn (Zea mays L.), very low tillering capacity, and very slow speed of regrowth after cutting. Consequently they are used nearly exclusively as a silage crop, never for hay production and only occasionally as direct pasture. Sudangrass in comparison is very grassy, characterized by very fine stems and narrow leaf blades, profuse tiller development, and exceptionally rapid recovery after cutting or grazing. Sudangrass (Sorghum bicolor ssp. sudanense L.) is an important forage species for pasture, grazing, green chop silage, hay and seed. Sudangrass is also referred to by the scientific name sorghum×drummondii (Steudel) Millsp. & Chase (=S. bicolor×S. arundinaceum) (R. F. Barnes and J. B. Beard (ed.), Glossary of Crop Science Terms, Crop Science Society of America, July 1992, pg. 84). Classification and species relationships of sorghum and sudangrass are discussed in several reports (Harlan and deWet, 1972; Celarier, 1958). For a comprehensive review of the floral characteristics, plant culture, and methods of self-pollinating or hybridizing sudangrass, see Shertz and Dalton, Sorghum 41:577-588, In Hybridization of Crop Plants, Fehr et al. (ed.), American Society of Agronomy Inc. (1980). Sorghum×sudangrass hybrids (Sorghum bicolor×S. bicolor spp. sudanese) which result from crossing a sorghum female with a sudangrass male are generally intermediate in character expression between sorghum and sudangrass. Sorghum×sudangrass hybrids are also commonly referred to as sorghum-sudangrass hybrids, sorghum/sudangrass, and SUDAX. Adding somewhat to the confusion of the nomenclature, those skilled in the art sometimes refer to sorghum×sudangrass hybrids as “sudangrass hybrids”. See, e.g., Miller and Stroup, 2003.
As a grain crop, Sorghum bicolor (L) Moench, is the fifth most important cereal after rice, wheat, maize, and barley. It constitutes the main food grain for over 750 million people who live in the semi-arid tropics of Africa, Asia, and Latin America. The largest group of producers are small-scale subsistence farmers with minimal access to production inputs such as fertiliser(s), pesticides, improved seeds (hybrids or varieties), good soil and water and improved credit facilities for their purchase.
There are many types of sorghum ranging in seed colour from white through red to brown. Traditional types are open-pollinated from which rural farmers retain seed for planting in the next season. Grain yields tend to be lower than the modern hybrids which are slowly being introduced. Commercial production of hybrid seed is a problem in many developing countries, and some rural farmers do not appreciate that harvested hybrid grain cannot be retained for planting the next season. Therefore they find sorghum production from hybrid seed expensive, even though the grain yields are higher than the land races. Resource-poor farmers prefer varieties incorporating the characteristics of resistance to insects, disease, drought, birds, and with acceptable yields of both grain for human consumption and fodder for livestock feed.
There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. These important traits may include higher seed yield, higher biomass yield, higher sugar yield, improved composition traits, improved conversion traits, resistance to diseases and insects, better stems and roots, tolerance to low temperatures, and better agronomic characteristics on grain quality.
Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F1 hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection, or a combination of these methods.
The complexity of inheritance influences choice of the breeding method. Backcross breeding is used to transfer one or a few favorable genes for a highly heritable trait into a desirable cultivar. This approach has been used extensively for breeding disease-resistant cultivars. Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.
Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).
Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial cultivars; those still deficient in a few traits may be used as parents to produce new populations for further selection. Inbred sorghum lines may be field tested in target area(s) for seed production for three or more years.
These processes, which lead to the final step of marketing and distribution of a sorghum hybrid, usually take from 8 to 12 years from the time the first cross is made and may rely on the development of improved breeding lines as precursors. Therefore, development of new cultivars and hybrids is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard cultivar. If a single observation is inconclusive, replicated observations provide a better estimate of its genetic worth.
The goal of sorghum plant breeding is to develop new, unique and superior sorghum lines and hybrids. The breeder initially selects and crosses two or more parental lines, followed by self-pollination and selection, producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing, and mutations. The breeder has no direct control at the cellular level. Therefore, two breeders will never develop the same line, or even very similar lines, having the same sorghum traits.
Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions, and further selections are then made, during and at the end of the growing season. The cultivars which are developed are unpredictable. This unpredictability is because the breeder's selection occurs in unique environments, with no control at the DNA level (using conventional breeding procedures), and with millions of different possible genetic combinations being generated. A breeder of ordinary skill in the art cannot predict the final resulting lines he develops, except possibly in a very gross and general fashion. The same breeder cannot produce the same line twice by using the exact same original parents and the same selection techniques. This unpredictability results in the expenditure of large amounts of research monies to develop superior new sorghum cultivars.
The development of new sorghum lines requires the development and selection of sorghum lines, the crossing of these lines and selection of superior hybrid crosses. The hybrid seed is produced by manual crosses between selected male-fertile parents or by using male sterility systems. Additional data on parental lines, as well as the phenotype of the hybrid, influence the breeder's decision whether to continue with the specific hybrid cross.
Pedigree breeding and recurrent selection breeding methods are used to develop cultivars from breeding populations. Breeding programs combine desirable traits from two or more cultivars or various broad-based sources into breeding pools from which cultivars are developed by selfing and selection of desired phenotypes. The new cultivars are evaluated to determine which have commercial potential.
Pedigree breeding is used commonly for the improvement of self-pollinating crops. Two parents which possess favorable, complementary traits are crossed to produce an F1. An F2 population is produced by selfing one or several F1's. Selection of the best individuals may begin in the F2 population; then, beginning in the F3, the best individuals in the best families are selected. Replicated testing of families can begin in the F4 generation to improve the effectiveness of selection for traits with low heritability. At an advanced stage of inbreeding (i.e., F6 and F7), the best lines or mixtures of phenotypically similar lines are tested for potential release as new cultivars.
Mass and recurrent selections can be used to improve populations of either self- or cross-pollinating crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.
Backcross breeding has been used to transfer genes for a simply inherited, highly heritable trait into a desirable homozygous cultivar or inbred line which is the recurrent parent. The source of the trait to be transferred is called the donor parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. After the initial cross, individuals possessing the phenotype of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent.
The single-seed descent procedure in the strict sense refers to planting a segregating population, harvesting a sample of one seed per plant, and using the one seed sample to plant the next generation. When the population has been advanced from the F2 to the desired level of inbreeding, the plants from which lines are derived will each trace to different F2 individuals. The number of plants in a population declines each generation due to failure of some seeds to germinate or some plants to produce at least one seed. As a result, not all of the F2 plants originally sampled in the population will be represented by a progeny when generation advance is completed.
Sorghum inbred lines are typically developed by first crossing two parent plants which may or may not be inbred. The parents may have traits which the breeder desires to combine. Typically, a few plants are chosen from the resulting segregating F2 population, and these plants are self pollinated for several generations in combination with selecting for increased uniformity and/or increased homozygosity. The resulting new inbred lines can then be tested with other inbred lines to determine combining ability and suitability as parents for hybrids. Utilizing male sterile parental lines, sorghum hybrids may be made that have two (single hybrid) or three (double hybrid) parents.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep, et. al, 1979; Fehr, 1987).
Proper testing should detect any major faults and establish the level of superiority or improvement over current lines and hybrids. In addition to showing superior performance, there must be a demand for a new line and hybrid that is compatible with industry standards or which creates a new market. The introduction of a new line or hybrid will incur additional costs to the seed producer, the grower, processor and consumer; for special advertising and marketing, altered seed and commercial production practices, and new product utilization. The testing preceding release of a new line or hybrid should take into consideration research and development costs as well as technical superiority of the final cultivar.
Sorghum, Sorghum bicolor (L.) Moench, is an important and valuable crop. Thus, a continuing goal of plant breeders is to develop stable, high yielding sorghum lines and hybrids that are agronomically sound. The reasons for this goal are obviously to maximize the amount of grain, biomass, sugar, biofuel/acre, and/or biopower/acre produced on the land used and to supply food and fuel for both animals and humans. To accomplish this goal, the sorghum breeder must select and develop sorghum plants that have the traits that result in superior lines and hybrids.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.